1. Field of the Disclosure
This specification relates to a delay device for checking a frequency modulated continuous wave (FMCW) radar, measuring a distance of a target and a relative velocity using microwaves and millimeter waves of a frequency modulated continuous waveform.
2. Background of the Disclosure
In general, a frequency modulated continuous wave (FMCW) radar is used for a radio altimeter, a proximity sensor, a sensor for preventing collision of vehicle and aircraft, an autonomous intelligent cruise control (AICC), an industrial level gauge, imaging, an indoor presence detection, and the like, to measure a distance and velocity of a target to be monitored.
The FMCW radar serves to change a frequency on a time basis using a frequency modulation. The FMCW radar may compute a distance and a relative velocity of a target by extracting an intermediate frequency fif (Hz), which is a difference frequency |ft−fr| between a transmission signal ft transmitted to the target and a return signal fr.
In order to check the FMCW radar, a virtual reception signal with time delayed as long as a specific distance from the target, has to be generated and applied to the FMCW radar.
FIG. 1 is a configuration view of a transceiver of a delay device for checking an FMCW radar using an RF frequency cable according to the related art.
In the related art, a plurality of radio frequency (RF) cables have been used to generate a time delay corresponding to a distance of a target. For example, referring to FIG. 1, when 6 RF cables 130 to 135 are combined with 12 RF switches 110 to 121, totally 6 bits (26), namely, 64 types of time delays may be generated.
However, when the RF cable extends, a cable loss may be increased. To compensate for the cable loss, there may be a need for a loss compensator including amplifiers 141 and 143 and a variable attenuator 142. Since different losses result from the 64 types of time delays, the variable attenuator 142 and the amplifiers 141 and 143 should be controlled separately.
Also, the RF cable has a property that the cable loss is drastically increased when volume and frequency thereof are increased. Hence, the RF cable may be inefficient when generating a time delay for a relatively remote target.
FIG. 2 is a configuration view of a transceiver of a delay device for checking an FMCW radar using an optical cable according to the related art.
As illustrated in FIG. 2, for a remote target, optical cables with a less loss and a small volume are used. As one example, when a delay device for checking an FMCW radar is configured by a combination of 6 optical cables 240 to 245 and 12 optical switches 220 to 231, the device has a cable loss less than the delay device illustrated in FIG. 1 but needs an E/O-O/E converter 210, 250 and a loss compensator 260 including an amplifier 261 and a variable attenuator 262. Specifically, the converter and the optical switches require for high costs.
As described above, the related art delay device needs a large number of delay cables, switches, amplifiers and converters to generate the time delay. Accordingly, the implementation of the device may be complicated and a fabricating cost thereof may thus increase.